Grinding disk



Patented Feb. 24, 1925.

UNITED STATES PATENT OFFICE.

SAMUEL M. BULLOCK, OF WILMETTE, AND HARRY S. LLOYD, F OAK PARK, ILLINOIS.

GRINDING DISK.

No Drawing.

To all whom it may concern:

Be it known that we, SAMUEL M. BUL- LOCK and HARRY S. LLOYD, citizens of the United States, and residents of the town of "Wilmette, in the county of Cook and State of Illinois, and the village of Oak Park, in the county of Cook and State of Illinois, respectively, have invented certain new and useful Improvements in Grinding Disks;

and we do hereby declare that the following is a full, clear, and exact description of the same.

This invention relates to the manufacture of an improved grinding disk and more par- W ticularly to those disks used for cutting or grinding soft metal or other like materials such as wood, and has for its object the production of a disk having an increased life by making the same thicker and less $0 liable to wear than ordinary glue, rubber,

or shellac abrasive disks.

In the manufacture of such grinding disks a bonding substance must be employed which will completely fill all the requisite quali fications, which are particularly numerous in connection with a disk used for grinding or cutting comparatively soft materials. Such a cementing or bonding material must bind the abrasive together with sufficient strength to withstand the pressure witlr which the material to be worked is applied thereto. and this bonding material must not soften by heat. It must not be so hard as to project above the surface of the disk, :5 or in other words it should wear away about as fast as does the abrasive. It must also be capable of being mixed uniformly throughout the abrasive so that the grinding surface may. be uniform in strength. texture and density. This bonding material must also be of such a nature that it will not spread over the surface of the abrasive or combine with the cuttings and form a glaze on the disk. This glazing is in fact 46 one of the most serious difficulties encountered in the use of grinding disks, especially for soft materials.

Many experiments have been conducted to Application filed March 7, 1921. Serial No. 45038054 devise a means of preventing this glazing and it has been found that the most effective method would be the use of a bonding material which would wear away under about the same amount of duty as is necessary to wear away the cutting angles of the abrasive, thus allowing the abrasive material to become detached from the wheel rather than remain upon it in a glazed condition and keeping the cutting surface presented to the work free from glaze and in a sharp c0ndition.

One object, therefore, of this invention is the construction of agrinding disk in which the bonding material employed is sufficiently hard to maintain the particles of abrasive in position as long as any cutting edges or angles remain thereon.

Another object of the invention is the con struction of a grinding disk where a binder is employed which will retain the abrasive material in cutting position and maintain the cutting action until the abrasive has been worn completely away, and which will be impervious to water.

Another important object of the invention' is the provision of a grinding disk which can be mounted upon a revolving wheel without much difliculty so that the flat side of the wheel can be used for grinding purposes, and it has been found that the employment of a cloth, wire or any fabric base for the application thereto of the abrasive by means of the particular bonding material as contemplated by this invention results in a grinding disk which is particularly adapted for such purposes.

A further important object of the invention is the manufacture of agrinding disk consisting wholly of abrasive and bonding material and which can be applied to a wheel either directly or by means of a'cloth, wire or other fabric backing by the use of glue or any like substance.

Still another important object of this invention is the manufacture of a grinding disk which can be applied to a grinding wheel by either glue or by means of the original binder which is used to maintain the abrasive in position upon the fabric disk.

Other and further important objects of this invention will be apparent from the disclosures in the accompanying specification. The invention (in a preferred form) is hereinafter more fully described.

Process:

In making these abrasive disks any suitable abrasive may be employed such as sand or other silicates, carborundum, emery, or alundum, and after the same has been reduced to the required fineness according to the character of work to be done is mixed with the improved binder of this invention which is chiefly composed of commercial calcium sulphate or Keenes cement. Plaster of Paris, calcined gypsum and flooring plaster, being practically all calcium sulphate, may also be used. It has been found that if small proportions of calcium carbonate, silica, and aluminum or some oxidizing agent are added to the calcium sulphate, not exceeding one to five per cent of each or sometimes merely a trace, the calcium sulphate will be able to exist in the resulting binder in two or more modifications which will behave differently with water. thereby resulting in the production of a binder which is peculiarly adapted to this particular form of grinding disk, being waterproof. All of the binder will eventually become hydrated but not all will set as plaster of Paris, it being probable that only those modified particles which possess the characteristic properties of forming a super-saturated solution will set and thus will allow the mass to crystallize in stages wherein the whole mass will become exceedingly hard with the abrasive imbedded therein.

In making up the mixture a suitable quantity of grains of the required abrasive is mixed in the proportion of two or three parts of grain to one part of the calcium sulphate or similar bondingmaterial. The bonding material and grain are mixed together dry and then enough water or some solvent containing a hardening or waterproofing agent added to dissolve the powder. The reason for mixing the bonding material and abrasive together .dry is so that the binder will be divided in equal proportions throughout the mass. After wetting with water, the composition is mixed thoroughly and then placed on a cloth, metal, or other fabric backing or any other suitable backing which may be desired, the

.method of applying same depending to a great degree upon the particular backing used, which in the case of a cloth or fabric may have to be wet with water or sometimes saturated with a solution of some suitable salt or other solvent in order to render the same more likely to retain the binder. The mixture is rolled, stamped or leveled to uniform thickness and allowed to stand until hard, whenthe completed disk -may be applied to a wheel and is ready for use.

If desired, the mixture may be molded to shape on a plate of glass, glazed paper or similar polished surface and the resulting molded disk applied to a wheel either with or without the use of a backing.

The action of this disk is far superior to shellac, rubber or glue disks now on the market, its Wearing properties being fully ten times as great. The particles being imbedded in the binder and each particle acts as a separate cutting agent, held in place by the rock-like binder.

If desired, the rate of setting of the binder may be retarded by the use of any organic substance such as glue, blood or some vegetable juice, which, being of a colloidal nature, will act to obstruct the growth of the crystals and delay the process of hydration and consequently the setting. The grinding disks may be applied to the revolvable wheel by means of glue or any other cement and they may also be attached to the Wheels by means of the same calcium sulphate binder Which is used in their construction. Water-glass or soluble sodium silicate may also be used to apply the grinding disks to the revolvable wheel either alone or in combination with the binder.

It will be seen that in case this disk becomes uneven through wear, the face of same can be dressed with an emery wheel dresseror similar tool, thus constituting an improvement over the ordinary disks used on the aforesaid materials.

We are aware that many other methods of constructing this disk and many other materials may also be used, and after the disclosures we have made, we do not purpose limiting the patent granted otherwise than necessitated by the prior art.

We claim as our invention:

1.'A grinding disk including a fabric backing and a layer of abrasive material, the particles of abrasive being secured to each other and to the fabric backing by a binder comprising hydrated calcium sulate.

p 2. A grinding disk impregnated with an abrasive mixed with a binder composed chiefly of anhydrous calcium sulphate, and including small portions of silica, calcium carbonate, aluminum and magnesium.

3. A grinding disk in which the binder is composed chiefly of calcium sulphate with a retarder added thereto.

4. The process of forming a grinding disk including mixing a suitable abrasive with a binder composed chiefly of calcium sulphate and a hardening agent, adding water thereto to form a paste, and allowing the same to harden.

5. A cutting disk including an abrasive In testimony whereof, we have hereunto and a, cement consisting principally of hysubscribed our names in the presence'of two drated calcium sulphate. subscribing witnesses.

6. A grinding disk in which the binder SAMUEL M. BULLOCK. is composed chiefly of calciumsulphate with a hardener added thereto. HARRY LLOYD 7. A grinding disk in which the binder Witnesses: is composed chiefly of calcium sulphate ALBERT J4 Fm,

with a water-proofing agent added thereto. JAMES M. OBnnin. 

